306 



ZOOLOGY 



SECT. 



intestinal blood-vessels of their host. Many free-living forms have 

 a sharp stylet for piercing the tissues of the plants on which they 

 feed, and a suctorial apparatus for absorbing the juices. The 



Fio. J 14— Ankylostoma duodenale. A, male and female in coitu. B, anterior eml, 

 showing — n\ gl. cervical glands ; ph. pharynx. C, mouth with spines ; D, posterior end of 

 male, with bursa. (After Leuckart.) 



posterior end of the pharynx is often dilated to form a globular 

 chamber with muscular walls, the gizzard (Fig. 246, gz.). The only 

 specially interesting variation in the structure of the intestine 

 is that occurring in Trichinella, one of the Nematodes parasitic 

 in Man, in which this part of the enteric canal consists of a single 

 row of perforated cells : the lumen is therefore not m^er-cellular 

 but m£ra-cellular, like the gullet of an Infusor. In the sexual stage 

 of Gordius the enteric canal undergoes more or less complete 

 degeneration. The alimentary canal in some rare cases has 



lh*J 



Fig. 245.— Transverse section of Gordius. bm. ventral nerve-cord; c. cuticle; et. epithelium 

 lining body-cavity ; hy. epiderm ; Ih. body-cavity ; Im. muscular layer ; md. intestine ; mes. 

 mesentery ; ov. ovary ; u. uterus. (From Lang, after Vejdovsky.) 



hollow appendages in the form of oesophageal glands or intestinal 

 cseca. In Dochmius a pair of pear-shaped bodies of unknown 

 function, the cervical glands (Fig. 244, B, cv. gl.), lie one on each 

 side of the pharynx and probably open externally near the mouth. 



